Detect Overlapping Stalls

You are given n stalls along with their coordinates in a 2D plane. Each stall is represented by its x and y coordinates. Your task is to determine whether any two stalls share the same coordinates.

Input Format: The input is read from standard input (stdin). The first line contains an integer n denoting the number of stalls. The following n lines each contain two space-separated integers representing the coordinates of a stall.

Output Format: Print a single line containing YES if there exists at least one pair of stalls with identical coordinates, and NO otherwise.

Example:

Input:
3
1 1
2 2
3 3

Output:
NO

In mathematical notation, if the set of stalls is given by \( \{(x_i,y_i) : i=1,2,\ldots,n \} \), determine if there exists indices \( i \neq j \) such that \( (x_i,y_i) = (x_j,y_j) \).

inputFormat

The first line of input contains an integer \( n \) indicating the number of stalls. Each of the next \( n \) lines contains two space-separated integers \( x \) and \( y \) representing the coordinates of a stall.

outputFormat

Output a single line containing YES if there exists at least one pair of overlapping stalls, otherwise output NO.

## sample

3
1 1
2 2
3 3

NO

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